1. Field of the Invention
The present patent application for industrial invention relates to a system used to reproduce the sound of a stringed instrument, in particular a piano, by means of modeling and digital synthesis of the oscillatory components, or partials, due to the excitation of the string constrained together with the other strings of the instrument, as in the case of the piano strings.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
The most common methodology used in the digital synthesis of the sound of musical instruments consists of storing a collection of sounds sampled from real musical instruments in the memory of a synthesis device. The samples can be pre-processed before storage and are successively reproduced in real time, during the synthesis, adding a post-processing that aims at adapting them to the player's requirements. Said processing modifies the recorded sounds in variable extent through dedicated computing resources, thus permitting proportional processing before storage. With the increase of computing resources, samples can be simplified in wavetable format or additionally reduced to few data in the memory according to wave-shaping techniques.
A methodology alternative to the use of samples provides for completely synthesizing the sound of the instrument by means of physical models. By simulating the dynamics of specific components of the musical instrument, these models imitate what happens in reality when a component typically identified as “exciter” stresses the remaining part of the model, identified as “resonator”. In the case of a piano, the use of hammer-string models based on digital waveguides is known, which are able to reproduce the motion of the string at the bridge, starting from the information on the impact velocity of the hammer on the string; then, the corresponding motion signal is processed by a discrete-time realization of a model of the soundboard without feedback effects on the string model (see Bank et al., EURASIP journal on Applied Signal Processing, vol. 2003, pp. 941-952, 2003).
In between the two aforementioned methodologies is the class of methods that make use of physical models, whose excitation is performed by injecting in the model a signal that is an indirect function of the force impressed by the player. With reference to the piano, the known models are the digital waveguide model excited by the hammer-soundboard-instrument body assembly (known as commuted synthesis, see Smith, U.S. Pat. No. 5,777,255), and the additive synthesis model of damped sinusoidal components informed by finite elements of the string-soundboard assembly, excited by signals measured directly from the piano, i.e. obtained from simulations made on physical models comparable to the ones described in the previous paragraph (see Guillaume, U.S. Pat. No. 7,915,515 B2).
The aforementioned prior art, in the context of piano simulation, does not provide for the realization of a method by means of a digital device, in which a scalable model of the strings (resonator) is stressed by a hammer model (exciter) according to the force impressed on the key by the player, thus generating a sound that is then sent to a post-processing step that takes into account the action of the soundboard-instrument body on the previously generated sound. The theoretical foundations of such a method are known from the literature (see Balázs Bank, Stefano Zambon, and Federico Fontana, pp 809-821, IEEE Transactions on Audio, Speech and Language Processing, Vol 18, No 4, May 2010): in particular, the same theory guarantees the rendering of all partials generated by the strings of a standard 88-key piano, as well as of the oscillatory components deriving from the longitudinal motion of the strings.
EP 2 261 891 discloses a method used to synthesize tone signals and a system used to generate tone signals, in particular for electronic pianola.
The primary purpose of the present invention is to eliminate the drawbacks of the prior art and realize a system based on the interconnection of a hammer, strings, and soundboard-instrument body model to synthesize digital piano sounds through the rendering of all oscillatory partial and transient longitudinal components of the instrument in different playing conditions.
An additional purpose is to provide a realization of the hammer, strings, and soundboard-instrument body model as much accurate as possible in terms of sound realism, and as much efficient as possible in terms of computational cost.
Another purpose is to provide a realization of the hammer and strings model allowing for fine tuning of the simulated instrument, similarly to what occurs in the real instrument when hammers and strings are tuned.